Measuring roughly 8.2 metres by 3.2 metres, it is a modest rectangle by any reckoning, yet the fact that it endured for centuries beneath the peat makes it quietly remarkable.

The platform was built in layers. A foundation of roundwood and brushwood, the kind of material cut from young branches and scrub, was laid down first to provide a stable base across the soft, waterlogged ground. On top of this came the main surface of heavier timbers. Peatland construction of this kind, sometimes called a trackway or working platform, was a practical solution to the problem of moving through or working on boggy terrain. What distinguishes Derryfadda is a detail found among the lower woodwork: two headed shafts made from cherry wood. The function of these objects is not spelled out in the record, but cherry was valued in early Irish woodworking for its density and fine grain, and the fact that these shafts were shaped, with formed heads, suggests they were fashioned with some deliberate purpose rather than thrown down as structural fill.